Our aim is to obtain a better understanding of the effect of cochlear hearing loss on the ability to hear signals in a noise background. Of particular interest is hearing ability in fluctuating background noises. Recent findings suggest that the normal auditory system analyzes information across an array of critical bands when detecting signals in fluctuating backgrounds. This type of signal analysis would appear to involve both spectral (across critical band) and temporal processing. One specific aim of the present project is to determine whether cochlear-impaired listeners suffer impairment of the spectro-temporal process in fluctuating noise. Because it is reasonable to assume that the spectro-temporal process may be degraded by poor frequency or temporal analysis, another specific aim of the project is to determine to what extent abnormal spectro-temporal processing may be related to more basic impairments of frequency and/or temporal resolution. The project will also investigate the effects signal frequency, fluctuation frequency, hearing loss severity, and hearing loss slope. The stimulus frequencies examined will be 0.5, 1.0, and 2.0 kHz. All stimuli will be delivered monaurally, over earphone. The tasks will include measures of detection in modulated noise as a function of modulation frequency and masker bandwidth, and measures of both frequency resolution (notched noise method) and temporal resolution (gap detection). Testing will be performed in a sound-treated room, using a forced-choice adaptive procedures. Subjects will include a normal-hearing control group (n=12), a group of listeners having mild to moderate, relatively flat cochlear hearing loss (n=25), a group of listeners having a more severe cochlear hearing loss (n-12), and a group having sloping hearing loss (n-12). Data will be analyzed using simple descriptive statistics, correlation, and analysis of covariance.